The present invention relates, in general, to electronics and, more particularly, to control circuits and methods.
In the past, motor driven translation systems have been used to control movement of mechanical systems using electrical signals. These types of systems have been used for controlling movement in a variety of systems including digital cameras, video recorders, and portable electronic devices. U.S. Patent Application Publication No. 2010/0201300 A1 published on Aug. 12, 2010 and filed by Colin Lyden et al. teaches a technique for generating a drive signal for a voice coil motor actuator that includes applying a test driving signal, receiving a back channel electric signal, and calculating the resonant frequency of the voice coil actuator from the back channel electric signal. The system uses the resonant frequency to create a drive signal for the voice coil actuator. Because this technique only uses the resonant frequency to generate the drive signal, it does not take into account different amplitude variations, which increases the settling time of the voice coil actuator. U.S. Patent Application Publication No. 2010/0201301 A1 published on Aug. 12, 2010 and filed by Colin Lyden et al. teaches a technique that addresses the increased settling time by using a pair of step signals that are sufficient to activate movement of a mechanical system and then place the mechanical system at a desired position. U.S. Patent Application Publication No. 2010/0201302 A1 published on Aug. 12, 2010 and filed by Colin Lyden et al. teaches a technique that uses a series of steps according to a selected row of Pascal's triangle. A drawback with these approaches is that the drive signals generated by these techniques have poor settling characteristics, e.g., the settling time is long.
Accordingly, it would be advantageous to have a circuit and a method for generating a drive signal having a fast settling time. It is desirable for the circuit and method to be cost and time efficient to implement.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference characters in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or an anode of a diode, and a control electrode means an element of the device that controls current flow through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain n-channel or p-channel devices, or certain n-type or p-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with embodiments of the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action and the initial action. The use of the words approximately, about, or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to about ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are regarded as reasonable variances from the ideal goal of being exactly as described.
It should be noted that a logic zero voltage level (VL) is also referred to as a logic low voltage or logic low voltage level and that the voltage level of a logic zero voltage is a function of the power supply voltage and the type of logic family. For example, in a Complementary Metal Oxide Semiconductor (CMOS) logic family a logic zero voltage may be thirty percent of the power supply voltage level. In a five volt Transistor-Transistor Logic (TTL) system a logic zero voltage level may be about 0.8 volts, whereas for a five volt CMOS system, the logic zero voltage level may be about 1.5 volts. A logic one voltage level (VH) is also referred to as a logic high voltage level, a logic high voltage, or a logic one voltage and, like the logic zero voltage level, the logic high voltage level also may be a function of the power supply and the type of logic family. For example, in a CMOS system a logic one voltage may be about seventy percent of the power supply voltage level. In a five volt TTL system a logic one voltage may be about 2.4 volts, whereas for a five volt CMOS system, the logic one voltage may be about 3.5 volts.